Any farmer will tell you that when it comes to efficiently growing food, compost is “black gold”. But some fear that fertilizer or compost made from human waste could be at risk of containing heavy metals, pathogens, or pharmaceuticals causing many environmentalists to consider it unsafe for enhancing plant growth. Others however, counter that contaminants are already part of our environment – they’re in the soil, water, and food we currently consume – and compost made from human wastes is no more unsafe than the soil that our food is already grown in. Fact is, no scientific evidence currently exists proving either stance is right or wrong.
To make compost from human waste, raw sewage is taken and mixed in with mulch. The carbon in the mulch speeds up the decomposition process, and generates heat. The material reaches 160 plus degrees and after 21 days (3 weeks), the generated heat is enough to kill off any harmful bacteria and pathogens that may have existed in the raw compost material. What could potentially remain however, is remnants of pharmaceutical products and heavy elements, both of which become concentrated in the food when human feces is used as fertilizer.
So for now it seems as if human waste is OK for compost if you can ensure the human sewage is derived from persons who remain free of pharmaceutical products. However, if the human waste comes from persons who use drugs or medicines, then the risk is unknown at this time. Regardless, using untreated human feces for fertilizer should be avoided unless extreme circumstances demand its use (it is normal for many South American and Asian countries to use human waste as fertilizers).